My local supermarket stocks arborio and carnaroli rices for making risotto, and also stocks "paella rice". I have, in the past, used them interchangeably in both risottos and paellas. Wikipedia handily summarises the difference between carnaroli and arborio here, but I can't find a description of the differences between these and a paella rice (aside from country of origin).

Note: I'm aware that the rice is cooked differently in a paella compared to a risotto -- I'm asking about the differences in the rice itself, not the cooking method.

3 Answers
3

'Paella rice' is not actually a variety of rice, but a category suitable, as the its name suggests, for making paella. Some common varieties are: Bahia, Balilla, Bomba, Senia, and Calasparra; the particular variety should be indicated on the packet that you choose.

These varieties differ from risotto rices, such as arborio and carnaroli, in not creating a creamy 'sauce' around the rice. Paella rice should stick together, but be distinct and not in a creamy 'sauce'.

Arborio rice has a creamy, chewy texture due to its higher amylopectin (one of two components in its starch) content. Paella rice absorbs more liquid than risotto rices, however it too would become 'creamy' if you stirred it like a risotto, since it also has a high starch content.

A grain of rice consists of a starchy wrapping around a core of protein. Risotto rice releases most of the starch quite readily, which is what gives risotto its creaminess (along with all the butter and parmesan). Each rice grain in risotto is thus relatively soft.

Paella rice holds onto its starch more, so generally is a bit more al dente - the protein core remains firm and the grains themselves remain relatively separate when compared to risotto.

I've found that cooking methods make a much greater difference than using either 'Paella' or 'Risotto' rice. I used to source rice for my Paella very carefully but I now buy risotto rice in bulk and I cannot tell the difference in the finished product. Providing that it is minimally stirred and not too much stock is added, risotto rice is perfectly adequate for Paella.